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  • Electronic Resource  (4)
  • 1980-1984  (2)
  • 1975-1979  (2)
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  • Electronic Resource  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    The effects of stem girdling on biogeochemical cycles within a mixed deciduous forest in eastern Tennessee (1979)
    Springer
    Oecologia 40 (1979), S. 247-257 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Studies on the effects of stem girdling of a tulip poplar (Liriodendron tulipifera L.) dominated mixed deciduous forest revealed that trees continued to grow above the point of girdling for more than two years after girdling. Soil core samples showed that root biomass was not significantly reduced until two years after trees were girdled. Litterfall during the fall of 1977 from trees girdled in Semptember 1975 and allowed to develop stump sprouts (plot no. 1) was 72% of the control plot. Litterfall during the same time from trees girdled in May 1976 but with stump sprouts removed (plot no. 2) was 82% of the control. Diameter growth during the growing season of 1977 was 53% of control in plot no. 1 and 68% of control in plot no. 2. No significant differences (P〉0.05) in forest floor CO2 efflux rates were observed between plots in the field. However, respiration rates were found to be higher in the girdled plot soil than in the control soil when roots and litter were removed by sieving and CO2 efflux from just the mineral soil and associated detritus was measured. Increased leaching rates of nutrients revealed the effects of girdling on biogeochemical cycles of the forest. The most pronounced effect was increased concentrations of NO3 ions in the soil water of the girdled plots, resulting in losses of NO3 ions below the root zone (〉60 cm) during the second year. These losses amounted to 25.4 kg ha-1 in plot no. 2 and 9.0 kg ha-1 in plot no. 1 as compared to 0.15 kg/ha-1 from the control plot. Calcium losses below the root zone during the second year were ≃10 kg ha-1 greater in plot no. 2 than the control plot, while losses from plot no. 1 were about equal to the control. Calcium and nitrogen uptake by the sprouts in plot no. 1 offset the slightly reduced uptake by the girdled trees and in fact uptake in plot no. 1 may have exceeded the control during the first year. Differences in uptake could account for only a portion of the differences in NO3 ion concentrations based on litterfall and diameter growth in girdled plots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00345322
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Age-related differences in the urinary excretion of prostaglandin F2α catabolites in the rat (1980)
    Springer
    Cellular and molecular life sciences 36 (1980), S. 635-637 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Tritium-labelled PGF2α was administered i.v. into rats of varying ages (2, 4, 6 weeks and adult). Urine was collected and assayed for radioactive products by thin-layer-chromatography. Results showed a distinctly different urinary profile between the 2-week-old and the adult rat. While the urinary pattern from the 2-week-old rat gave a single less polar product than PGF2α, the pattern from the adult rat gave products more polar than PGF2α. Urine from the 4- and 6-week-old rats gave a mixture of these types of products. These results indicate that some prostaglandin catabolic pathway (likely the ω-oxidative system) is activated in vivo within the 4–6-week postnatal period in the rat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01970104
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The effects of stem girdling on biogeochemical cycles within a mixed deciduous forest in eastern Tennessee (1979)
    Springer
    Oecologia 40 (1979), S. 259-271 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Nitrogen mineralization and net nitrification rates were 3–7 times greater in soil incubations from a girdled Liriodendron tulipifera (L.) stand than in a control stand. Neither litter nor root extracts had an inhibitory effect on nitrogen mineralization or nitrification rate. A lack of nitrification inhibitors also was demonstrated by the fact that ammonium added to the control stand was completely converted to nitrate upon incubation. Additions of sucrose increased CO2 evolution and decreased nitrogen mineralization and nitrification rates in the girdled plot soil, suggesting that nitrification could be effectively controlled by competition for NH 4 + supplies by heterotrophic soil organisms. CO2 evolution rates during incubation showed that heterotrophic as well as nitrifier activities were greater in the girdled plot soil than in the ungirdled plot soil, but the ratio of C to N mineralized was lower in the girdled plot soil. These results collectively indicate that nitrification is regulated by the availability of NH 4 + in these stands, and that the latter is strongly regulated by heterotrophic demand for N.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00345323
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Altered purine and pyrimidine metabolism in erythrocytes with purine nucleoside phosphorylase deficiency (1980)
    Springer
    Biochemical genetics 18 (1980), S. 221-234 
    Details
    ISSN: 1573-4927
    Keywords: purine nucleotide degradation ; PP-ribose-P ; deoxynucleosides ; orotic acid ; hypoxanthine-guaninine phosphoribosyltransferase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Purine and pyrimidine metabolism was compared in erythrocytes from three patients from two families with purine nucleoside phosphorylase deficiency and T-cell immunodeficiency, one heterozygote subject for this enzyme deficiency, one patient with a complete deficiency of hypoxanthine-guanine phosphoribosyltransferase, and two normal subjects. The erythrocytes from the heterozygote subject were indistinguishable from the normal erythrocytes. The purine nucleoside phosphorylase deficient erythrocytes had a block in the conversion of inosine to hypoxanthine. The erythrocytes with 0.07% of normal purine nucleoside phosphorylase activity resembled erythrocytes with hypoxanthine-guanine phosphoribosyltransferase deficiency by having an elevated intracellular concentration of PP-ribose-P, increased synthesis of PP-ribose-P, and an elevated rate of carbon dioxide release from orotic acid during its conversion to UMP. Two hypotheses to account for the associated immunodeficiency—that the enzyme deficiency leads to a block of PP-ribose-P synthesis or inhibition of pyrimidine synthesis—could not be supported by observations in erythrocytes from both enzyme-deficient families.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00484238
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    Paper (German National Licenses)
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